U.S. patent application number 14/395123 was filed with the patent office on 2015-03-12 for symmetric-type ups power system based on a nine-phase phase-shifting autotransformer.
This patent application is currently assigned to GUANGDONG EAST POWER CO., LTD. The applicant listed for this patent is GUANGDONG EAST POWER CO., LTD.. Invention is credited to Zhaoyang Tang, Jiarong Wang, Haibo Xu, Shengfa Zhang.
Application Number | 20150069955 14/395123 |
Document ID | / |
Family ID | 46563806 |
Filed Date | 2015-03-12 |
United States Patent
Application |
20150069955 |
Kind Code |
A1 |
Xu; Haibo ; et al. |
March 12, 2015 |
SYMMETRIC-TYPE UPS POWER SYSTEM BASED ON A NINE-PHASE
PHASE-SHIFTING AUTOTRANSFORMER
Abstract
A symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer includes a three-phase AC power
input terminal, a three-phase AC power output terminal, a
nine-phase phase-shift autotransformer, a synchronized control
device for controlling output of a three-phase inverter, a
power-frequency isolation transformer and three circuits of output
devices; wherein the three-phase AC input terminal of the
nine-phase phase-shifting autotransformer is connected to the
three-phase AC power input terminal, each circuit of the output
devices includes a zero-sequence suppression commutating inductor,
a three-phase six-pulse rectifier, a three-phase inverter and a
filter inductor which are connected with each other in sequence,
each circuit of the zero-sequence suppression commutating inductor
is connected to the three-phase AC output terminal of the
phase-shifting autotransformer, each circuit of the filter inductor
is connected to the input terminal of the power-frequency isolation
transformer.
Inventors: |
Xu; Haibo; (Dongguan,
CN) ; Zhang; Shengfa; (Dongguan, CN) ; Wang;
Jiarong; (Dongguan, CN) ; Tang; Zhaoyang;
(Dongguan, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GUANGDONG EAST POWER CO., LTD. |
Dongguan, Guangdong |
|
CN |
|
|
Assignee: |
GUANGDONG EAST POWER CO.,
LTD
Dongguan, Guangdong
CN
|
Family ID: |
46563806 |
Appl. No.: |
14/395123 |
Filed: |
September 27, 2012 |
PCT Filed: |
September 27, 2012 |
PCT NO: |
PCT/CN2012/082210 |
371 Date: |
October 17, 2014 |
Current U.S.
Class: |
320/107 ;
307/23 |
Current CPC
Class: |
H02J 9/06 20130101; Y02E
40/10 20130101; H01F 30/12 20130101; H01F 38/14 20130101; Y02E
40/40 20130101; H02J 7/02 20130101; H02M 5/453 20130101; H02J 5/00
20130101; H02J 3/01 20130101 |
Class at
Publication: |
320/107 ;
307/23 |
International
Class: |
H01F 38/14 20060101
H01F038/14; H02J 7/02 20060101 H02J007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 20, 2012 |
CN |
201210117736.8 |
Claims
1. A symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer, comprising a three-phase AC power
input terminal, a three-phase AC power output terminal, a
nine-phase phase-shift autotransformer, a synchronized control
device for controlling output of a three-phase inverter, a
power-frequency isolation transformer and three circuits of output
devices; wherein the nine-phase phase-shift autotransformer is a
symmetric-type nine-phase phase-shift autotransformer, a
three-phase AC input terminal of the nine-phase phase-shifting
autotransformer is connected to the three-phase AC power input
terminal; the nine-phase phase-shifting autotransformer is provided
with three groups of three-phase AC output terminals, namely output
terminals A1, B1 and C1 in an advance group, output terminals A0,
B0 and C0 in an original group, and output terminals A2, B2 and C2
in a hysteresis group respectively; the power-frequency isolation
transformer is provided with three groups of three-phase input
terminals, namely input terminals U1, V1 and W1 in an advance
group, input terminals U0, V0 and W0 in an original group, and
input terminals U2, V2 and W2 in a hysteresis group respectively;
the output terminals U, V and W of the power-frequency isolation
transformer are connected to the three-phase AC power output
terminal; the three circuits of output devices are an output device
in an advance group, an output device in an original group and an
output device in a hysteresis group; the output device in an
advance group comprising a zero-sequence suppression commutating
inductor in an advance group, a three-phase six-pulse rectifier in
an advance group, a three-phase inverter in an advance group and a
filter inductor in an advance group which are connected to each
other in sequence; three-phase input terminals of the zero-sequence
suppression commutating inductor in an advance group are connected
to the output terminals A1, B1 and C1 in an advance group;
three-phase AC output terminals of the filter inductor in an
advance group are connected to the input terminals U1, V1 and W1 in
an advance group; the output device in an original group comprising
a zero-sequence suppression commutating inductor in an original
group, a three-phase six-pulse rectifier in an original group, a
three-phase inverter in an original group and a filter inductor in
an original group which are connected to each other in sequence;
three-phase input terminals of the zero-sequence suppression
commutating inductor in an original group are connected to the
output terminals A0, B0 and C0 in an original group; three-phase AC
output terminals of the filter inductor in an original group are
connected to the input terminals U0, V0 and W0 in an original
group; the output device in a hysteresis group comprising a
zero-sequence suppression commutating inductor in a hysteresis
group, a three-phase six-pulse rectifier in a hysteresis group, a
three-phase inverter in a hysteresis group and a filter inductor in
a hysteresis group which are connected to each other in sequence;
three-phase input terminals of the zero-sequence suppression
commutating inductor in a hysteresis group are connected to the
output terminals A2, B2 and C2 in a hysteresis group; three-phase
AC output terminals of the filter inductor in a hysteresis group
are connected to the input terminals U2, V2 and W2 in a hysteresis
group; the synchronized control device is provided with four groups
of sampling input terminals respectively connected to the
three-phase AC power input terminal, the output terminal of the
three-phase inverter in an advance group, the output terminal of
the three-phase inverter in an original group and the output
terminal of the three-phase inverter in a hysteresis group; the
synchronized control device is provided with three groups of
control output terminals respectively connected to the control
terminal of the three-phase inverter in an advance group, the
control terminal of the three-phase inverter in an original group
and the control terminal of the three-phase inverter in a
hysteresis group.
2. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 1, wherein the
power-frequency isolation transformer is a three-phase transformer
characterized by coupled isolation of power-frequency four ports
and Y/Y connection, the power-frequency isolation transformer is
provided with a U-phase magnetic pillar, a V-phase magnetic pillar
and a W-phase magnetic pillar, each of which is provided with three
independent and identical input windings and a output winding,
constituting an output mode for coupled isolation of four ports in
which the connection between the primary winding and the secondary
winding is a "Y/Y" structure; the input windings on the U-phase
magnetic pillar are respectively connected to U1 phase outputted by
the three-phase inverter in an advance group, U0 phase outputted by
the three-phase inverter in an original group and U2 phase
outputted by the three-phase inverter in a hysteresis group; the
output winding on the U-phase magnetic pillar is U-phase output;
the input windings on the V-phase magnetic pillar are respectively
connected to V1 phase outputted by the three-phase inverter in an
advance group, V0 phase outputted by the three-phase inverter in an
original group and V2 phase outputted by the three-phase inverter
in a hysteresis group; the output winding on the V-phase magnetic
pillar is V-phase output; the input windings on the W-phase
magnetic pillar are respectively connected to W1 phase outputted by
the three-phase inverter in an advance group, W0 phase outputted by
the three-phase inverter in an original group and W2 phase
outputted by the three-phase inverter in a hysteresis group; the
output winding on the W-phase magnetic pillar is W-phase
output.
3. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 2, further comprising an
energy storage device; wherein the energy storage device comprises
a charger, a storage battery and a coupling unit for controlling
directional migration of electric current; three-phase AC input
terminal of the charger is connected to the three-phase AC power
input terminal, DC output terminal of the charger is connected to
the storage battery; the coupling unit comprising six diodes, in
which, anodes of three diodes are connected to the anode of the
storage battery, cathodes of the three diodes are respectively
connected to the anode at DC input terminal of the three-phase
inverter in an advance group, the anode at DC input terminal of the
three-phase inverter in an original group and the anode at DC input
terminal of the three-phase inverter in a hysteresis group;
cathodes of the other three diodes are respectively connected to
the cathode of the storage battery, anodes of the other three
diodes are respectively connected to the cathode at DC input
terminal of the three-phase inverter in an advance group, the
cathode at DC input terminal of the three-phase inverter in an
original group and the cathode at DC input terminal of the
three-phase inverter in a hysteresis group; voltages at DC input
terminal of the three-phase inverter in an advance group, DC input
terminal of the three-phase inverter in an original group and DC
input terminal of the three-phase inverter in a hysteresis group
are more than voltage of the storage battery.
4. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 3, wherein the energy
storage device also comprises contactors JK1, JK2 and JK3; two
diodes D1 and D2 respectively connected to the anode and the
cathode at DC input terminal of the three-phase inverter in an
advance group are diodes in an advance group; two diodes D3 and D4
respectively connected to the anode and the cathode at DC input
terminal of the three-phase inverter in an original group are
diodes in an original group; two diodes D5 and D6 respectively
connected to the anode and the cathode at DC input terminal of the
three-phase inverter in a hysteresis group are diodes in a
hysteresis group; the two diodes Dl and D2 in an advance group are
respectively connected in parallel to the main contact of the
contactor JK1; the two diodes D3 and D4 in an original group are
respectively connected in parallel to the main contact of the
contactor JK2; the two diodes D5 and D6 in a hysteresis group are
respectively connected in parallel to the main contact of the
contactor JK3.
5. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 4, further comprising a
bypass circuit; wherein the bypass circuit comprises a bypass
static switching device, the output terminal of the bypass static
switching device is connected to the three-phase AC power input
terminal.
6. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 5, wherein circuits of the
three-phase six-pulse rectifier in an advance group, the
three-phase six-pulse rectifier in an original group and the
three-phase six-pulse rectifier in a hysteresis group are
controllable three-phase rectifier circuits. The controllable
three-phase rectifier circuits comprising an inductor package
consisting of three inductors, six unilateral thyristors and a
capacitor. In the six unilateral thyristors, every two of which are
connected in tandem series to each other to form three subcircuits,
both ends of each subcircuit are respectively connected to the
anode and the cathode of the capacitor and thus forming a return
circuit, one end of each of the three inductors is respectively
connected to middle potential terminals of the three subcircuits,
and the other end of each of the three inductors is respectively
connected to input terminals of the controllable three-phase
rectifier circuits.
7. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 6, wherein circuits of the
three-phase inverter in an advance group, the three-phase inverter
in an original group and the three-phase inverter in a hysteresis
group are three-phase full-bridge inverter circuits; the
three-phase full-bridge inverter circuits consist of three
single-phase full-bridge circuits, each of the three single-phase
full-bridge circuits comprising an upper bridge arm and a lower
bridge arm, both of which respectively consist of two insulated
gate bipolar transistors; wherein, collectors of two insulated gate
bipolar transistors of the upper bridge arm are connected to the
anodes at the DC input terminals of the three-phase full-bridge
inverter circuits, emitting electrodes of the two insulated gate
bipolar transistors of the upper bridge arm are respectively
connected to collectors of two insulated gate bipolar transistors
of the lower bridge arm; emitting electrodes of the two insulated
gate bipolar transistors of the lower bridge arm are respectively
connected to the cathodes at the DC input terminals of the
three-phase full-bridge inverter circuits; two output ports at the
output terminal of each of the three single-phase full-bridge
circuits are respectively connected to two connection points of the
upper bridge arm and the lower bridge arm of the single-phase
full-bridge circuit.
8. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 7, wherein circuits of the
filter inductor in an advance group, the filter inductor in an
original group and the filter inductor in a hysteresis group are LC
low-pass filter circuits connected to output terminals of the
single-phase full-bridge circuits; the LC low-pass filter circuits
comprising three filter circuits, each of which consists
essentially of an inductor and a capacitor and is provided with two
input terminals and two output terminals; both input terminals of
each of the three filter circuits are respectively connected to the
midpoints of bridge arms of the single-phase full-bridge circuits,
serving as an input port; both output terminals of each of the
three filter circuits serve as an output port, which is
respectively connected to corresponding three-phase AC input port
of the power-frequency isolation transformer via a fuse.
9. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 8, wherein a main circuit
static switching device is arranged between the power-frequency
isolation transformer and the three-phase AC power output terminal;
the main circuit static switching device consists essentially of
three bidirectional thyristors; one end of each of the three
bidirectional thyristors is connected to the three-phase AC output
terminal of the power-frequency isolation transformer, and the
other end of each of the three bidirectional thyristors is
respectively connected to the three-phase AC power output
terminal.
10. The symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer of claim 9, wherein the bypass
static switching device consists essentially of three bidirectional
thyristors; one end of each of the three bidirectional thyristors
is connected to the input terminal of the bypass circuit, and the
other end of each of the three bidirectional thyristors is
respectively connected to the three-phase AC power output terminal.
Description
FIELD OF THE INVENTION
[0001] The invention belongs to the technical field of a power
supply, and particularly relates to the technical field of a
high-power power-frequency uninterruptible power supply (UPS), in
particular to a symmetric-type UPS power system based on a
nine-phase phase-shifting autotransformer.
BACKGROUND OF THE INVENTION
[0002] Demands for high-power power-frequency uninterruptible power
supply (UPS) are very large in global industrialization and
informatization economic construction. In the field of
medium-high-power UPS, the power-frequency UPS has the advantages
of good adaptive capacity to power supply environment, high
reliability and strong shock resistance of load capacity and the
like, thus being widely used in all industries and fields.
Particularly, independent and stable zero potential unique to the
power-frequency UPS provides a guarantee for safety use of the
high-power UPS. Grid-side current of a conventional power-frequency
UPS has large current harmonic, which causes serious pollution to
power grid; at present, high-power UPS is configured with a power
grid compensation device and the like so as to meet the
requirements for use of power grid.
[0003] In order to solve the problem of power harmonic pollution
resulted from input side rectification of the conventional
high-power power-frequency UPS, a full-isolation phase-shifting
transformer based on ".DELTA./Y-type and .DELTA./.DELTA.-type
structure" and a multi-pulse rectifier structure of a balance
reactor are adopted for input of a high-power system. For example,
12-pulse rectification technology is achieved by two conventional
6-pulse phase-controlled rectifiers connected in parallel with a
phase-shift angle of 30.degree. so as to suppress quintuple or
septuple harmonic produced by a three-phase six-pulse rectifier.
The method has the problem of high cost and the full-isolation
phase-shifting transformer is large and heavy, inconvenient for
extending of power unit of a higher-power AC-DC rectifier. 18-pulse
rectification technology can further reduce grid-side current
harmonic, a nine-phase phase-shift power supply thereof is realized
usually by an isolation transformer, which has disadvantages of
bulky isolation transformer and low economic benefit.
SUMMARY OF THE INVENTION
[0004] The invention solves shortcomings of the prior art by
providing a symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer. The UPS power system effectively
reduces grid-side input current harmonic of the AC-DC rectifier,
suppresses quintuple, septuple, elevenfold and thirteenfold
harmonic, and reduces content of seventeenfold and ninteenfold
harmonic, small in size and low in cost.
[0005] In order to achieve the above-mentioned objectives, the
invention adopts such a technical scheme as below:
[0006] A symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer includes a three-phase AC power
input terminal, a three-phase AC power output terminal, a
nine-phase phase-shift autotransformer, a synchronized control
device for controlling output of a three-phase inverter, a
power-frequency isolation transformer and three circuits of output
devices; wherein the nine-phase phase-shift autotransformer is a
symmetric-type nine-phase phase-shift autotransformer, a
three-phase AC input terminal of the nine-phase phase-shifting
autotransformer is connected to the three-phase AC power input
terminal; the nine-phase phase-shifting autotransformer is provided
with three groups of three-phase AC output terminals, namely output
terminals A1, B1 and C1 in an advance group, output terminals A0,
B0 and C0 in an original group, and output terminals A2, B2 and C2
in a hysteresis group respectively; the power-frequency isolation
transformer is provided with three groups of three-phase input
terminals, namely input terminals U1, V1 and W1 in an advance
group, input terminals U0, V0 and W0 in an original group, and
input terminals U2, V2 and W2 in a hysteresis group respectively;
the output terminals U, V and W of the power-frequency isolation
transformer are connected to the three-phase AC power output
terminal; the three circuits of output devices are an output device
in an advance group, an output device in an original group and an
output device in a hysteresis group; the output device in an
advance group includes a zero-sequence suppression commutating
inductor in an advance group, a three-phase six-pulse rectifier in
an advance group, a three-phase inverter in an advance group and a
filter inductor in an advance group which are connected to each
other in sequence; three-phase input terminals of the zero-sequence
suppression commutating inductor in an advance group are connected
to the output terminals A1, B1 and C1 in an advance group;
three-phase AC output terminals of the filter inductor in an
advance group are connected to the input terminals U1, V1 and W1 in
an advance group; the output device in an original group includes a
zero-sequence suppression commutating inductor in an original
group, a three-phase six-pulse rectifier in an original group, a
three-phase inverter in an original group and a filter inductor in
an original group which are connected to each other in sequence;
three-phase input terminals of the zero-sequence suppression
commutating inductor in an original group are connected to the
output terminals A0, B0 and C0 in an original group; three-phase AC
output terminals of the filter inductor in an original group are
connected to the input terminals U0, VO and W0 in an original
group; the output device in a hysteresis group includes a
zero-sequence suppression commutating inductor in a hysteresis
group, a three-phase six-pulse rectifier in a hysteresis group, a
three-phase inverter in a hysteresis group and a filter inductor in
a hysteresis group which are connected to each other in sequence;
three-phase input terminals of the zero-sequence suppression
commutating inductor in a hysteresis group are connected to the
output terminals A2, B2 and C2 in a hysteresis group; three-phase
AC output terminals of the filter inductor in a hysteresis group
are connected to the input terminals U2, V2 and W2 in a hysteresis
group; the synchronized control device is provided with four groups
of sampling input terminals respectively connected to the
three-phase AC power input terminal, the output terminal of the
three-phase inverter in an advance group, the output terminal of
the three-phase inverter in an original group and the output
terminal of the three-phase inverter in a hysteresis group; the
synchronized control device is provided with three groups of
control output terminals respectively connected to the control
terminal of the three-phase inverter in an advance group, the
control terminal of the three-phase inverter in an original group
and the control terminal of the three-phase inverter in a
hysteresis group.
[0007] Further, the power-frequency isolation transformer is a
three-phase transformer characterized by coupled isolation of
power-frequency four ports and Y/Y connection, the power-frequency
isolation transformer is provided with a U-phase magnetic pillar, a
V-phase magnetic pillar and a W-phase magnetic pillar, each of
which is provided with three independent and identical input
windings and a output winding, constituting an output mode for
coupled isolation of four ports in which the connection between the
primary winding and the secondary winding is a "Y/Y" structure; the
input windings on the U-phase magnetic pillar are respectively
connected to U1 phase outputted by the three-phase inverter in an
advance group, U0 phase outputted by the three-phase inverter in an
original group and U2 phase outputted by the three-phase inverter
in a hysteresis group; the output winding on the U-phase magnetic
pillar is U-phase output; the input windings on the V-phase
magnetic pillar are respectively connected to V1 phase outputted by
the three-phase inverter in an advance group, V0 phase outputted by
the three-phase inverter in an original group and V2 phase
outputted by the three-phase inverter in a hysteresis group; the
output winding on the V-phase magnetic pillar is V-phase output;
the input windings on the W-phase magnetic pillar are respectively
connected to W1 phase outputted by the three-phase inverter in an
advance group, W0 phase outputted by the three-phase inverter in an
original group and W2 phase outputted by the three-phase inverter
in a hysteresis group; the output winding on the W-phase magnetic
pillar is W-phase output.
[0008] Further, the symmetric-type UPS power system based on a
nine-phase phase-shifting autotransformer also includes an energy
storage device; the energy storage device includes a charger, a
storage battery and a coupling unit for controlling directional
migration of electric current; three-phase AC input terminal of the
charger is connected to the three-phase AC power input terminal, DC
output terminal of the charger is connected to the storage battery;
the coupling unit includes six diodes, in which, anodes of three
diodes are connected to the anode of the storage battery, cathodes
of the three diodes are respectively connected to the anode at DC
input terminal of the three-phase inverter in an advance group, the
anode at DC input terminal of the three-phase inverter in an
original group and the anode at DC input terminal of the
three-phase inverter in a hysteresis group; cathodes of the other
three diodes are respectively connected to the cathode of the
storage battery, anodes of the other three diodes are respectively
connected to the cathode at DC input terminal of the three-phase
inverter in an advance group, the cathode at DC input terminal of
the three-phase inverter in an original group and the cathode at DC
input terminal of the three-phase inverter in a hysteresis group;
voltages at DC input terminal of the three-phase inverter in an
advance group, DC input terminal of the three-phase inverter in an
original group and DC input terminal of the three-phase inverter in
a hysteresis group are more than voltage of the storage
battery.
[0009] Further, the energy storage device also includes contactors
JK1, JK2 and JK3; two diodes D1 and D2 respectively connected to
the anode and the cathode at DC input terminal of the three-phase
inverter in an advance group are diodes in an advance group; two
diodes D3 and D4 respectively connected to the anode and the
cathode at DC input terminal of the three-phase inverter in an
original group are diodes in an original group; two diodes D5 and
D6 respectively connected to the anode and the cathode at DC input
terminal of the three-phase inverter in a hysteresis group are
diodes in a hysteresis group; the two diodes D1 and D2 in an
advance group are respectively connected in parallel to the main
contact of the contactor JK1; the two diodes D3 and D4 in an
original group are respectively connected in parallel to the main
contact of the contactor JK2; the two diodes D5 and D6 in a
hysteresis group are respectively connected in parallel to the main
contact of the contactor JK3.
[0010] Further, the symmetric-type UPS power system based on a
nine-phase phase-shifting autotransformer also includes a bypass
circuit; the bypass circuit includes a bypass static switching
device, the output terminal of the bypass static switching device
is connected to the three-phase AC power input terminal.
[0011] Further, circuits of the three-phase six-pulse rectifier in
an advance group, the three-phase six-pulse rectifier in an
original group and the three-phase six-pulse rectifier in a
hysteresis group are controllable three-phase rectifier circuits.
The controllable three-phase rectifier circuits includes an
inductor package consisting of three inductors, six unilateral
thyristors and a capacitor. In the six unilateral thyristors, every
two of which are connected in tandem series to each other to form
three subcircuits, both ends of each subcircuit are respectively
connected to the anode and the cathode of the capacitor and thus
forming a return circuit, one end of each of the three inductors is
respectively connected to middle potential terminals of the three
subcircuits, and the other end of each of the three inductors is
respectively connected to input terminals of the controllable
three-phase rectifier circuits.
[0012] Further, circuits of the three-phase inverter in an advance
group, the three-phase inverter in an original group and the
three-phase inverter in a hysteresis group are three-phase
full-bridge inverter circuits; the three-phase full-bridge inverter
circuits consist of three single-phase full-bridge circuits, each
of the three single-phase full-bridge circuits includes an upper
bridge arm and a lower bridge arm, both of which respectively
consist of two insulated gate bipolar transistors; wherein,
collectors of two insulated gate bipolar transistors of the upper
bridge arm are connected to the anodes at the DC input terminals of
the three-phase full-bridge inverter circuits, emitting electrodes
of the two insulated gate bipolar transistors of the upper bridge
arm are respectively connected to collectors of two insulated gate
bipolar transistors of the lower bridge arm; emitting electrodes of
the two insulated gate bipolar transistors of the lower bridge arm
are respectively connected to the cathodes at the DC input
terminals of the three-phase full-bridge inverter circuits; two
output ports at the output terminal of each of the three
single-phase full-bridge circuits are respectively connected to two
connection points of the upper bridge arm and the lower bridge arm
of the single-phase full-bridge circuit.
[0013] Further, circuits of the filter inductor in an advance
group, the filter inductor in an original group and the filter
inductor in a hysteresis group are LC low-pass filter circuits
connected to output terminals of the single-phase full-bridge
circuits; the LC low-pass filter circuits include three filter
circuits, each of which consists essentially of an inductor and a
capacitor and is provided with two input terminals and two output
terminals; both input terminals of each of the three filter
circuits are respectively connected to the midpoints of bridge arms
of the single-phase full-bridge circuits, serving as an input port;
both output terminals of each of the three filter circuits serve as
an output port, which is respectively connected to corresponding
three-phase AC input port of the power-frequency isolation
transformer via a fuse.
[0014] Further, a main circuit static switching device is arranged
between the power-frequency isolation transformer and the
three-phase AC power output terminal; the main circuit static
switching device consists essentially of three bidirectional
thyristors; one end of each of the three bidirectional thyristors
is connected to the three-phase AC output terminal of the
power-frequency isolation transformer, and the other end of each of
the three bidirectional thyristors is respectively connected to the
three-phase AC power output terminal
[0015] Further, the bypass static switching device consists
essentially of three bidirectional thyristors; one end of each of
the three bidirectional thyristors is connected to the input
terminal of the bypass circuit, and the other end of each of the
three bidirectional thyristors is respectively connected to the
three-phase AC power output terminal.
[0016] Beneficial effects obtained in the invention are as below: a
symmetric-type UPS power system based on a nine-phase
phase-shifting autotransformer includes a three-phase AC power
input terminal, a three-phase AC power output terminal, a
nine-phase phase-shift autotransformer, a synchronized control
device for controlling output of a three-phase inverter, a
power-frequency isolation transformer and three circuits of output
devices; a three-phase AC input terminal of the nine-phase
phase-shifting autotransformer is connected to the three-phase AC
power input terminal; the nine-phase phase-shifting autotransformer
is provided with three groups of three-phase AC output terminals,
namely output terminals A1, B1 and C1 in an advance group, output
terminals A0, B0 and C0 in an original group, and output terminals
A2, B2 and C2 in a hysteresis group respectively; the
power-frequency isolation transformer is provided with three groups
of three-phase AC input terminals, namely input terminals U1, V1
and W1 in an advance group, input terminals U0, V0 and W0 in an
original group, and input terminals U2, V2 and W2 in a hysteresis
group respectively; the output terminals U, V and W of the
power-frequency isolation transformer are connected to the
three-phase AC power output terminal; the three circuits of output
devices are an output device in an advance group, an output device
in an original group and an output device in a hysteresis group;
the output device in an advance group includes a zero-sequence
suppression commutating inductor in an advance group, a three-phase
six-pulse rectifier in an advance group, a three-phase inverter in
an advance group and a filter inductor in an advance group which
are connected to each other in sequence; three-phase input
terminals of the zero-sequence suppression commutating inductor in
an advance group are connected to the output terminals A1, B1 and
C1 in an advance group; three-phase AC output terminals of the
filter inductor in an advance group are connected to the input
terminals U1, V1 and W1 in an advance group; the output device in
an original group includes a zero-sequence suppression commutating
inductor in an original group, a three-phase six-pulse rectifier in
an original group, a three-phase inverter in an original group and
a filter inductor in an original group which are connected to each
other in sequence; three-phase input terminals of the zero-sequence
suppression commutating inductor in an original group are connected
to the output terminals A0, B0 and C0 in an original group;
three-phase AC output terminals of the filter inductor in an
original group are connected to the input terminals U0, VO and W0
in an original group; the output device in a hysteresis group
includes a zero-sequence suppression commutating inductor in a
hysteresis group, a three-phase six-pulse rectifier in a hysteresis
group, a three-phase inverter in a hysteresis group and a filter
inductor in a hysteresis group which are connected to each other in
sequence; three-phase input terminals of the zero-sequence
suppression commutating inductor in a hysteresis group are
connected to the output terminals A2, B2 and C2 in a hysteresis
group; three-phase AC output terminals of the filter inductor in a
hysteresis group are connected to the input terminals U2, V2 and W2
in a hysteresis group; the synchronized control device is provided
with four groups of sampling input terminals respectively connected
to the three-phase AC power input terminal and the output terminals
of the three-phase inverter in an advance group, the three-phase
inverter in an original group and the three-phase inverter in a
hysteresis group; the synchronized control device is provided with
three groups of control output terminals respectively connected to
the control terminal of the three-phase inverter in an advance
group, the control terminal of the three-phase inverter in an
original group and the control terminal of the three-phase inverter
in a hysteresis group.
[0017] The invention is characterized by:
[0018] (1) A nine-phase phase-shifting autotransformer with a
uniquely symmetric structure whose rated power not exceeding 17% of
the total output power of the system.
[0019] (2) The system topology of a parallel structure guarantees
independent running of the AC power supply with three groups of
phase position with a mutual phase difference of 20o, so as to
provide identical power to load, thus accurately achieving
"18-pulse rectification" of the whole power system and effectively
reducing current harmonic of power grid.
[0020] (3) DC/AC inverter of the parallel structure guarantees
balance of three parallel channels and constitutes redundant design
of the system, with a high reliability of the whole system.
[0021] (4) The uniquely designed the power-frequency "three-phase
transformer characterized by coupled isolation of power-frequency
four ports and Y/Y connection" realizes isolated coupling of AC
output of three independent and parallel channels, leads to an
independent output of the three-phase transformer, suitable for
unbalance load.
[0022] (5) The power-frequency power system is not provided with a
balance reactor, designed standardly and symmetrically with high
redundancy rate; the topological structure thereof is suitable for
UPS power systems with a wide power range and a capacity more than
500 KVA.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a structure diagram of the invention;
[0024] FIG. 2 is a structure diagram of windings of the nine-phase
phase-shifting autotransformer in the invention;
[0025] FIG. 3 is a structure diagram of windings of the
power-frequency isolation transformer in the invention;
[0026] FIG. 4 is a schematic diagram of the three-phase inverter
circuits in the invention; and
[0027] FIG. 5 is a schematic diagram of the invention.
REFERENCE NUMERALS OF DRAWINGS
[0028] 1--the nine-phase phase-shifting autotransformer; 2--the
zero-sequence suppression commutating inductor in an advance
group;
[0029] 3--the zero-sequence suppression commutating inductor in an
original group; 4--the zero-sequence suppression commutating
inductor in a hysteresis group;
[0030] 5--the three-phase six-pulse rectifier in an advance group;
6--the three-phase six-pulse rectifier in an original group; 7--the
three-phase six-pulse rectifier in a hysteresis group;
[0031] 8--the three-phase inverter in an advance group; 9--the
three-phase inverter in an original group;
[0032] 10--the three-phase inverter in a hysteresis group; 11--the
filter inductor in an advance group;
[0033] 12--the filter inductor in an original group; 13--the filter
inductor in a hysteresis group;
[0034] 14--the synchronized control device; 15--the power-frequency
isolation transformer;
[0035] 16--the coupling unit; 17--the charger; 18--the three-phase
AC power output terminal;
[0036] 19--the input terminal of the bypass circuit; 20--the
storage battery.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0037] Further description of the invention is made in conjunction
with the accompanying drawings and embodiments.
[0038] Embodiment: as shown in FIGS. 1-4, a symmetric-type UPS
power system based on a nine-phase phase-shifting autotransformer 1
includes a three-phase AC power input terminal, a three-phase AC
power output terminal 18, a nine-phase phase-shift autotransformer
1, a synchronized control device 14 for controlling output of a
three-phase inverter, a power-frequency isolation transformer 15
and three circuits of output devices. The nine-phase phase-shift
autotransformer 1 is a symmetric-type nine-phase phase-shift
autotransformer 1, a three-phase AC input terminal of the
nine-phase phase-shifting autotransformer 1 is connected to the
three-phase AC power input terminal; the nine-phase phase-shifting
autotransformer 1 is provided with three groups of three-phase AC
output terminals, namely output terminals A1, B1 and C1 in an
advance group, output terminals A0, B0 and C0 in an original group,
and output terminals A2, B2 and C2 in a hysteresis group
respectively. The power-frequency isolation transformer 15 is
provided with three groups of three-phase AC input terminals,
namely input terminals U1, V1 and W1 in an advance group, input
terminals U0, V0 and W0 in an original group, and input terminals
U2, V2 and W2 in a hysteresis group respectively; the output
terminals U, V and W of the power-frequency isolation transformer
15 are connected to the three-phase AC power output terminal 18;
the three circuits of output devices are an output device in an
advance group, an output device in an original group and an output
device in a hysteresis group; the output device in an advance group
includes a zero-sequence suppression commutating inductor 2 in an
advance group, a three-phase six-pulse rectifier 5 in an advance
group, a three-phase inverter 8 in an advance group and a filter
inductor 11 in an advance group which are connected to each other
in sequence; three-phase input terminals of the zero-sequence
suppression commutating inductor 2 in an advance group are
connected to the output terminals A1, B1 and C1 in an advance
group; three-phase AC output terminals of the filter inductor 11 in
an advance group are connected to the input terminals U1, V1 and W1
in an advance group; the output device in an original group
includes a zero-sequence suppression commutating inductor 3 in an
original group, a three-phase six-pulse rectifier 6 in an original
group, a three-phase inverter 9 in an original group and a filter
inductor 12 in an original group which are connected to each other
in sequence; three-phase input terminals of the zero-sequence
suppression commutating inductor 3 in an original group are
connected to the output terminals A0, B0 and C0 in an original
group; three-phase AC output terminals of the filter inductor 12 in
an original group are connected to the input terminals U0, V0 and
W0 in an original group; the output device in a hysteresis group
includes a zero-sequence suppression commutating inductor 4 in a
hysteresis group, a three-phase six-pulse rectifier 7 in a
hysteresis group, a three-phase inverter 10 in a hysteresis group
and a filter inductor 13 in a hysteresis group which are connected
to each other in sequence; three-phase input terminals of the
zero-sequence suppression commutating inductor 4 in a hysteresis
group are connected to the output terminals A2, B2 and C2 in a
hysteresis group; three-phase AC output terminals of the filter
inductor 13 in a hysteresis group are connected to the input
terminals U2, V2 and W2 in a hysteresis group. The synchronized
control device is provided with four groups of sampling input
terminals respectively connected to the three-phase AC power input
terminal and the output terminals of the three-phase inverter in an
advance group, the three-phase inverter in an original group and
the three-phase inverter in a hysteresis group; the synchronized
control device is provided with three groups of control output
terminals respectively connected to the control terminal of the
three-phase inverter in an advance group, the control terminal of
the three-phase inverter in an original group and the control
terminal of the three-phase inverter in a hysteresis group.
[0039] Input symmetric three-phase AC power supply (A, B and C) is
subject to a phase shift by the nine-phase phase-shift
autotransformer 1 as three groups of symmetric three-phase AC power
supplies with a mutual phase difference of 20o: an original group
(A0, B0 and C0), an advance group (A1, B1 and C1) and a hysteresis
group (A2, B2 and C2). The phase position in an original group (A0,
B0 and C0) is identical to the input three-phase AC power supply
(A, B and C), a phase difference of 20o is arranged between the
advance group (A1, B1 and C1) and the original group (A0, B0 and
C0); a phase difference of 20o is arranged between the hysteresis
group (A2, B2 and C2) and the original group (A0, B0 and C0).
[0040] As shown in FIG. 1, signals of the original group (A0, B0
and C0), the advance group (A1, B1 and C1) and the hysteresis group
(A2, B2 and C2) are transmitted through the corresponding
zero-sequence suppression commutating inductor and the
corresponding three-phase six-pulse rectifier for achieving
six-pulse rectification respectively, and finally outputted to the
corresponding three-phase inverter and the corresponding filter
inductor, and then subject to AC isolation and parallel connection
and power synthesis for output by the power-frequency isolation
transformer 15. The zero-sequence suppression commutating inductor
has a function of suppressing zero-sequence current, convenient for
commutation of current in the three-phase six-pulse rectifier.
[0041] FIG. 2 shows a construction of windings and connection
diagram of the 18-pulse.+-.20o phase-shifting autotransformer
adopted by the invention, namely the nine-phase phase-shifting
autotransformer 1. In FIG. 2, the original group (A0, B0 and C0) is
input of the transformer, connected to 380V three-phase AC supply
of mains supply; (A1, B1 and C1) and (A2, B2 and C2) are two
three-phase AC outputs respectively. A phase angle of 20o is
arranged between the advance group (A1, B1 and C1) and the original
group (A0, B0 and C0), and a phase angle of 20o is arranged between
the original group (A0, B0 and C0) and the hysteresis group (A2, B2
and C2). The original group (A0, B0 and C0) of the transformer is
connected to three-phase network voltage (A, B and C) for proper
functioning. In this way, for achieving 18-pulse rectification
effect, power capacity of the nine-phase phase-shifting
autotransformer 1 is not more than 20% of the total output power of
the system, the nine-phase phase-shifting autotransformer 1 is much
less than a conventional isolation power-frequency phase-shifting
transformer in terms of structure and weight.
[0042] Further, the power-frequency isolation transformer 15 is a
three-phase transformer characterized by coupled isolation of
power-frequency four ports and Y/Y connection, the power-frequency
isolation transformer 15 is provided with three groups of AC input
ports and a group of AC output port, one each of the magnetic
pillars of the power-frequency isolation transformer 15 is provided
with three sections of independent windings which constitute a
group of three-phase AC input port, both ends of each section of
independent windings are two input terminals of a three-phase AC
input port; the connection between the primary winding and the
secondary winding of the power-frequency isolation transformer 15
is a "Y/Y" structure.
[0043] FIG. 3 shows a diagrammatic drawing of the three-phase
transformer structure characterized by coupled isolation of four
ports and Y/Y connection. In the FIG. 3, [U1, U0 and U2] are
respectively reference phase outputs of initial phase angle 00 in
the three-phase sinusoidal output of three channels DC/AC
inverters, which are controlled to be identical waveform and
in-phase with three-phase network mains input. In accordance with
winding configuration in FIG. 3, both input and output are of
Y/Y-type structures, no-load voltage ratio of the output voltage U
to three input voltages is w2/w1, the output current is subject to
superposition of three-phase [U1, U0 and U2] input current, namely
power superposition. In the same way, the design approach is
applicable to the relation between V-phase output and three-phase
input [V1, V0 and V2], and applicable to the relation between
W-phase output and three-phase input [W1, W0 and W2].
[0044] Further, the UPS power system based on a nine-phase
phase-shifting autotransformer 1 also includes an energy storage
device; the energy storage device includes a charger 17, a storage
battery 20 and a coupling unit 16 for controlling directional
migration of electric current. Three-phase AC input terminal of the
charger 17 is connected to the three-phase AC power input terminal,
DC output terminal of the charger 17 is connected to the storage
battery 20. The coupling unit 16 includes six diodes, in which,
anodes of three diodes are connected to the anode of the storage
battery 20, cathodes of the three diodes are respectively connected
to the anode at DC input terminal of the three-phase inverter 8 in
an advance group, the anode at DC input terminal of the three-phase
inverter 9 in an original group and the anode at DC input terminal
of the three-phase inverter 10 in a hysteresis group. Cathodes of
the other three diodes are respectively connected to the cathode of
the storage battery 20, anodes of the other three diodes are
respectively connected to the cathode at DC input terminal of the
three-phase inverter 8 in an advance group, the cathode at DC input
terminal of the three-phase inverter 9 in an original group and the
cathode at DC input terminal of the three-phase inverter 10 in a
hysteresis group. Voltages at DC input terminal of the three-phase
inverter 8 in an advance group, DC input terminal of the
three-phase inverter 9 in an original group and DC input terminal
of the three-phase inverter 10 in a hysteresis group are more than
voltage of the storage battery 20.
[0045] In actual operation, under normal circumstance, voltage of
the storage battery 20 is slightly less than direct voltage output
of the three-phase six-pulse rectifiers, having no effect on two DC
output terminals of the three-phase six-pulse rectifier. In case of
power outage, the storage battery 20 supplies power to the
three-phase inverters via a diode unidirectional access.
[0046] Further, the energy storage device also includes contactors
JK1, JK2 and JK3; two diodes D1 and D2 respectively connected to
the anode and the cathode at DC input terminal of the three-phase
inverter 8 in an advance group are diodes in an advance group; two
diodes D3 and D4 respectively connected to the anode and the
cathode at DC input terminal of the three-phase inverter 9 in an
original group are diodes in an original group; two diodes D5 and
D6 respectively connected to the anode and the cathode at DC input
terminal of the three-phase inverter 10 in a hysteresis group are
diodes in a hysteresis group. The two diodes D1 and D2 in an
advance group are respectively connected in parallel to the main
contact of the contactor JK1; the two diodes D3 and D4 in an
original group are respectively connected in parallel to the main
contact of the contactor JK2; the two diodes D5 and D6 in a
hysteresis group are respectively connected in parallel to the main
contact of the contactor JK3.
[0047] Contactors JK1, JK2 and JK3 are designed to reduce energy
consumption of the coupling unit 16; for example, contactors JK1,
JK2 and JK3 are at off-state when the system runs properly, and
contactors JK1, JK2 and JK3 are at on-state when the power grid is
subject to power outage, the storage battery 20 directly supplies
power to the three-phase inverters, the coupling unit 16 is at
short-circuit condition, thus reducing energy consumption of the
coupling unit 16.
[0048] Further, the UPS power system based on a nine-phase
phase-shifting autotransformer 1 also includes a bypass circuit;
the bypass circuit includes a bypass static switching device, the
output terminal of the bypass static switching device is connected
to the three-phase AC power output terminal 18.
[0049] The bypass circuit is designed to increase stability of the
system. The bypass static switching device is closed and directly
supplies power via the bypass circuit when the three-phase
inverters break down; the input terminal 19 of the bypass circuit
is directly connected to mains supply or other power supply
units.
[0050] Further, circuits of the three-phase six-pulse rectifier 5
in an advance group, the three-phase six-pulse rectifier 6 in an
original group and the three-phase six-pulse rectifier 7 in a
hysteresis group are controllable three-phase rectifier circuits.
The controllable three-phase rectifier circuits include an inductor
package consisting of three inductors, six unilateral thyristors
and a capacitor. In the six unilateral thyristors, every two of
which are connected in tandem series to each other to form three
subcircuits, both ends of each subcircuit are respectively
connected to the anode and the cathode of the capacitor and thus
forming a return circuit, one end of each of the three inductors is
respectively connected to middle potential terminals of the three
subcircuits, and the other end of each of the three inductors is
respectively connected to input terminals of the controllable
three-phase rectifier circuits. Here, the input terminals of the
controllable three-phase rectifier circuits equivalently serve as
the input terminal of the three-phase six-pulse rectifier 5 in an
advance group, or the three-phase six-pulse rectifier 6 in an
original group or the three-phase six-pulse rectifier 7 in a
hysteresis group.
[0051] Further, circuits of the three-phase inverter 8 in an
advance group, the three-phase inverter 9 in an original group and
the three-phase inverter 10 in a hysteresis group are three-phase
full-bridge inverter circuits. The three-phase full-bridge inverter
circuits consist of three single-phase full-bridge circuits, each
of the three single-phase full-bridge circuits includes an upper
bridge arm and a lower bridge arm, both of which respectively
consist of two insulated gate bipolar transistors; wherein,
collectors of two insulated gate bipolar transistors of the upper
bridge arm are connected to the anodes at the DC input terminals of
the three-phase full-bridge inverter circuits, emitting electrodes
of the two insulated gate bipolar transistors of the upper bridge
arm are respectively connected to collectors of two insulated gate
bipolar transistors of the lower bridge arm; emitting electrodes of
the two insulated gate bipolar transistors of the lower bridge arm
are respectively connected to the cathodes at the DC input
terminals of the three-phase full-bridge inverter circuits; two
output ports at the output terminal of each of the three
single-phase full-bridge circuits are respectively connected to two
connection points of the upper bridge arm and the lower bridge arm
of the single-phase full-bridge circuit.
[0052] Under normal conditions, a heavy-current balance reactor of
large inductive coupling is used for achieving parallel connection
of direct current side output of the three groups of six-pulse
rectifiers, in this way, the economic benefit from the 18-pulse
rectifier is offset. Three parallel and independent inverter
channels (see FIG. 1) with identical main circuits instead of bulky
balance reactors are respectively adopted in the invention, in this
way, the three groups of six-pulse rectifiers are impossible to
form ring current via the direct current side, the nine-phase
phase-shifting autotransformer accurately achieves 18-pulse
rectification, greatly reducing input current harmonic.
[0053] In FIG. 1, the synchronized control device 14 guarantees the
parallel and independent inverter channels to run according to the
same rule, outputs three-phase voltage with the same phase
frequency, phase position and amplitude, and guarantees three-phase
voltage output (U, V and W) synchronized with network voltage input
(A, B and C).
[0054] The invention, by adopting a three-phase full-bridge
structure, not only improves the system reliability and redundancy
capacity, but also provides the system with stronger unbalance load
capacity, conducive to modularized and normative design of the
system.
[0055] Further, circuits of the filter inductor 11 in an advance
group, the filter inductor 12 in an original group and the filter
inductor 13 in a hysteresis group are LC low-pass filter circuits
connected to output terminals of the single-phase full-bridge
circuits; the LC low-pass filter circuits include three filter
circuits, each of which consists essentially of an inductor and a
capacitor and is provided with two input terminals and two output
terminals; both input terminals of each of the three filter
circuits are respectively connected to the midpoints of bridge arms
of the single-phase full-bridge circuits, serving as an input port;
both output terminals of each of the three filter circuits serve as
an output port, which is respectively connected to corresponding
three-phase AC input port of the power-frequency isolation
transformer via a fuse.
[0056] Further, a main circuit static switching device is arranged
between the power-frequency isolation transformer 15 and the
three-phase AC power output terminal 18; the main circuit static
switching device consists essentially of three bidirectional
thyristors; one end of each of the three bidirectional thyristors
is connected to the three-phase AC output terminal of the
power-frequency isolation transformer 15, and the other end of each
of the three bidirectional thyristors is respectively connected to
the three-phase AC power output terminal 18.
[0057] Further, the bypass static switching device consists
essentially of three bidirectional thyristors; one end of each of
the three bidirectional thyristors is connected to the input
terminal of the bypass circuit, and the other end of each of the
three bidirectional thyristors is respectively connected to the
three-phase AC power output terminal 18.
[0058] Further description of the invention is made in conjunction
with the accompanying drawing 5.
[0059] As shown in FIG. 5, T1 is the nine-phase phase-shifting
autotransformer of 18-pulse.+-.20.degree.. The controllable
three-phase rectifier in an advance group consists of L1, SCR1,
SCR3, SCRS, SCR4, SCR6, SCR2 and C1; the three-phase inverter in an
advance group consists of IGBT1.about.IGBT12; the three
single-phase inverted full-bridge LC low-pass filter circuits of
the inverter in an advance group consist of L4, C4, L5, C5, L6 and
C6. In the same way, the three-phase six-pulse rectifier in an
original group consists of L2, SCR1', SCR3', SCRS', SCR4', SCR6',
SCR2' and C2; the three-phase inverter in an original group
consists of IGBT13.about.IGBT24; the three single-phase inverted
full-bridge LC low-pass filter circuits of the inverter in an
original group consist of L7, C7, L8, C8, L9 and C9; the
three-phase six-pulse rectifier in a hysteresis group consists of
L3, SCR1'', SCR3'', SCRS'', SCR4'', SCR6'', SCR2'' and C3; the
three-phase inverter in a hysteresis group consists of
IGBT25.about.IGBT36; the three single-phase inverted full-bridge LC
low-pass filter circuits of the inverter in a hysteresis group
consist of L10, C10, L11, C11, L12 and C12. T2 is the three-phase
transformer characterized by coupled isolation of four ports; power
superposition is achieved by the power-frequency isolation
transformer 15 for output of the single-phase full-bridge inverters
in an advance group, in an original group and in a hysteresis
group. SCR7-9 are bypass static switches and SCR10-12 are inverter
static switches.
[0060] Under the circumstance of normal rectification input
three-phase supply, three-phase current is transmitted, through a
rectifier input breaker CB1, FUSE1-3 and hall current sensors HP1-3
for detecting rectifier input current, to the input terminal of a
18-pulse.+-.20.degree. phase-shifting autotransformer, the input
three-phase AC power supply is subject to a phase shift by the
phase-shift autotransformer as three groups of three-phase AC power
supplies with a mutual phase difference of 20.degree.: an advance
group (U1, V1 and W1), an original group (U0, V0 and W0) and a
hysteresis group (U2, V2 and W2). (In FIG. 5, zero-sequence
suppression commutating inductors are omitted). The three-phase AC
current in an advance group (U1, V1 and W1) is transmitted through
and rectified into DC current by the controllable three-phase
rectifier in an advance group, transmitted through and inverted
into AC current by the three-phase inverter in an advance group,
and then output pure three-phase current by the LC low-pass filter
circuit. In the same way, The three-phase AC current in an original
group (U0, V0 and W0) is transmitted through and rectified into DC
current by the three-phase six-pulse rectifier in an original
group, transmitted through and inverted into AC current by the
three-phase inverter in an original group, and then output pure
three-phase current by the LC low-pass filter circuit. The
three-phase AC current in a hysteresis group (U2, V2 and W2) is
transmitted through and rectified into DC current by the
three-phase six-pulse rectifier in a hysteresis group, transmitted
through and inverted into AC current by the three-phase inverter in
a hysteresis group, and then output pure three-phase current by the
LC low-pass filter circuit. Under the control of the synchronized
control device 14 (not drawn in FIG. 5), the three groups of AC
current output of the same frequency and the same phase with a
bypass input AC power supply, with a small difference of amplitude,
are transmitted through the three-phase transformer characterized
by coupled isolation of four ports for power superposition, and
then transmitted through the inverter static switch and an output
breaker CB3 to supply power to loads. At the same time, the
rectification input three-phase supply charges the storage battery
20 via the isolation charger 17.
[0061] Under the circumstance of abnormal operation of the
rectification input three-phase supply, the three-phase six-pulse
rectifier in an advance group, the three-phase six-pulse rectifier
in an original group and the three-phase six-pulse rectifier in a
hysteresis group stop running The storage battery supplies power to
the three-phase inverter in an advance group via the diodes D1, D2
and JK1, supplies power to the three-phase inverter in an original
group via the diodes D3, D4 and JK2, and supplies power to the
three-phase inverter in a hysteresis group via the diodes D5, D6
and JK3 so as to guarantee the three groups of inverters to work
uninterruptedly and to supply power to loads uninterruptedly. Once
the rectification input three-phase supply returns to normal, the
three-phase six-pulse rectifier in an advance group, the
three-phase six-pulse rectifier in an original group and the
three-phase six-pulse rectifier in a hysteresis group also returns
to normal operation, diodes JK1, JK2 and JK3 are disconnected, and
the charger 17 returns to normal operation. Due to certain
redundancy of the UPS system, when any group of three-phase
six-pulse rectifier or three-phase inverter breaks down, the others
still can work normally. The UPS system is adaptable to 100%
imbalance loads due to adoption of the three-phase full-bridge
inverter circuit consisting of three single-phase full-bridge
circuits. For example, when none of the three groups of three-phase
inverters can work normally, the three-phase static switches
SCR10-12 for inverter output are switched off; the bypass
three-phase static switches SCR7-9 are switched on. Due to the same
frequency and the same phase of inverter three-phase current output
with the bypass AC power input, the UPS can be switched to the
bypass uninterruptedly; CB3 is a bypass input breaker. When the UPS
is required for maintenance, a maintenance bypass of the UPS is
used to supply power to loads uninterruptedly; CB4 is a breaker of
the maintenance bypass.
[0062] The above-mentioned embodiment is a preferred embodiment of
the application, equivalent technical scheme based on the
embodiment is within the scope of protection of the
application.
* * * * *